The present invention relates to a relational algebra engine which performs a set operation at high speed in a data base system which deals with a relational model.
When a data base system is to be established, abstract data of the real world must be modeled. Data models which are conventionally proposed include hierarchical model, network model and relational model. Among these models, the relational model is most promising. A concept of relation in mathematical set theory is applied to this model.
ln data base systems which utilize the hierarchical model and the network model, data is strung by the chain of pointers. Therefore, the data structure more or less depends on an application program. On the other hand, in a data base system utilizng the relational model, data is expressed as a set so that the data structure is simple and each data is highly independent. ln other words, the relational data base system has an advantage in that, even if part of the data base is modified, the application program thereof is not influenced. From this point of view, an extensive study has been made for implementing the relational model to establish a data base system of large capacity and a knowledge data base system.
General purpose computers which are currently used are designed to perform arithmetic operations at high speed. Therefore, the relational data base processing must be executed with software in the general purpose computer. In a data base which deals with a large amount of data, the application program becomes very complex and the processing time thereof becomes long. It has been desired, therefore, that hardware for effectively performing the set operation of the relational model in a data base system be developed.